Function

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Overview

Plays a role in T-cell activation and in the adaptive immune response. Regulates the proliferation of activated T-cells. Regulates the release of cytokines and IFNG by activated T-cells. Mediates the response of T-cells toward infected and transformed cells that are characterized by high levels of phosphorylated metabolites, such as isopentenyl pyrophosphate.

Human Vγ9Vδ2 T cells are well known for their rapid and potent response to infection and tumorigenesis when in the presence of endogenous or exogenous phosphoisoprenoids. However, the molecular mechanisms behind the activation of this γδ T cell population remains unclear. Evidence pointing to a role for the CD277/butyrophilin-3 (BTN3A) molecules in this response led us to investigate the structures of these molecules and their modifications upon binding to an agonist antibody (20.1) that mimics phosphoisoprenoid-mediated Vγ9Vδ2 activation and an antagonist antibody (103.2) that inhibits this reactivity. We find that the three BTN3A isoforms: BTN3A1, BTN3A2, and BTN3A3, have high structural homology to the B7 superfamily of proteins and exist as V-shaped homodimers in solution, associating through the membrane proximal C-type Ig domain. The 20.1 and 103.2 antibodies bind to separate epitopes on the BTN3A Ig-V domain with high affinity but likely with different valencies based on their binding orientation. These structures directly complement functional studies of this system that demonstrate that BTN3A1 is necessary for Vγ9Vδ2 activation and begin to unravel the extracellular events that occur during stimulation through the Vγ9Vδ2 T cell receptor.

Human peripheral Vγ9Vδ2 T cells are activated by phosphorylated metabolites (phosphoagonists [PAg]) of the mammalian mevalonate or the microbial desoxyxylulose-phosphate pathways accumulated by infected or metabolically distressed cells. The underlying mechanisms are unknown. We show that treatment of nonsusceptible target cells with antibody 20.1 against CD277, a member of the extended B7 superfamily related to butyrophilin, mimics PAg-induced Vγ9Vδ2 T-cell activation and that the Vγ9Vδ2 T-cell receptor is implicated in this effect. Vγ9Vδ2 T-cell activation can be abrogated by exposing susceptible cells (tumor and mycobacteria-infected cells, or aminobisphosphonate-treated cells with up-regulated PAg levels) to antibody 103.2 against CD277. CD277 knockdown and domain-shuffling approaches confirm the key implication of the CD277 isoform BTN3A1 in PAg sensing by Vγ9Vδ2 T cells. Fluorescence recovery after photobleaching (FRAP) experiments support a causal link between intracellular PAg accumulation, decreased BTN3A1 membrane mobility, and ensuing Vγ9Vδ2 T-cell activation. This study demonstrates a novel role played by B7-like molecules in human γδ T-cell antigenic activation and paves the way for new strategies to improve the efficiency of immunotherapies using Vγ9Vδ2 T cells.

The human butyrophilin (BTN) 3 or CD277 molecules belong to the B7 family members and are expressed in various immune cells such as T and NK cells. Here, we show that CD277 triggering considerably enhances TCR-induced cytokine production and cell proliferation, even when another co-stimulatory molecule, CD28, is engaged. These CD277-induced additive functional effects are in accordance with the detection of early T-cell activation events such as TCR-induced cell signaling being increased upon CD277 engagement. However, we found that CD277 triggering is not involved in CD16- or NKp46-induced NK cell activation. BTN3/CD277 comprises three structurally related members, BTN3A1, BTN3A2 and BTN3A3. CD277 antibodies recognize all isoforms and we describe a differential expression of BTN3 isoforms between T and NK cells that could explain differential CD277 functions between T and NK cells. Our results show that, while T cells express all BTN3/CD277 transcripts, NK cells express mostly BTN3A2, which lacks the B30.2 intracellular domain. Furthermore, NKp30-induced cytokine production is decreased by the specific engagement of BTN3A2, but not by BTN3A1 triggering. Thus, we provide new insights into the CD277 co-stimulatory pathway that may differentially participate in the regulation of various cell-mediated immune responses.

CD277, a member of the butyrophilin subfamily 3 (BTN3), shares significant sequence similarities and predicted common structural features with inhibitory B7-H4 and other members of the B7 superfamily. Here we report that CD277 is consistently expressed in stromal, as well as tumor cells in the microenvironment of human advanced ovarian carcinoma specimens, both of primary and metastatic origin. MHC-II+ myeloid antigenpresenting leukocytes (dendritic cells and macrophages) express significantly higher levels of surface CD277, compared to other tumor-infiltrating leukocyte subsets, and this expression is significantly up-regulated by multiple common tumor microenvironmental signals, including VEGF and CCL3. Most importantly, engagement of CD277 on the surface of TCR-stimulated T cells inhibits their otherwise robust expansion and production of Th1 cytokines by preventing the up-regulation of cFLIP. Our results point to a role for CD277 up-regulated by microenvironmental signals in the acquisition of a regulatory phenotype by tumor-associated myeloid cells. Consequently, CD277, and likely other butyrophilins and butyrophilin-like molecules, emerge as regular players in the orchestration of immunosuppressive networks in ovarian cancer, and therefore new targets for interventions to overcome immune evasion and boost anti-tumor immunity in cancer patients.

Characterization of the extracellular protein interactome has lagged far behind that of intracellular proteins, where mass spectrometry and yeast two-hybrid technologies have excelled. Improved methods for identifying receptor-ligand and extracellular matrix protein interactions will greatly accelerate biological discovery in cell signaling and cellular communication. These technologies must be able to identify low-affinity binding events that are often observed between membrane-bound coreceptor molecules during cell-cell or cell-extracellular matrix contact. Here we demonstrate that functional protein microarrays are particularly well-suited for high-throughput screening of extracellular protein interactions. To evaluate the performance of the platform, we screened a set of 89 immunoglobulin (Ig)-type receptors against a highly diverse extracellular protein microarray with 686 genes represented. To enhance detection of low-affinity interactions, we developed a rapid method to assemble bait Fc fusion proteins into multivalent complexes using protein A microbeads. Based on these screens, we developed a statistical methodology for hit calling and identification of nonspecific interactions on protein microarrays. We found that the Ig receptor interactions identified using our methodology are highly specific and display minimal off-target binding, resulting in a 70% true-positive to false-positive hit ratio. We anticipate that these methods will be useful for a wide variety of functional protein microarray users.

The human butyrophilin (BTN) 3 or CD277 molecules belong to the B7 family members and are expressed in various immune cells such as T and NK cells. Here, we show that CD277 triggering considerably enhances TCR-induced cytokine production and cell proliferation, even when another co-stimulatory molecule, CD28, is engaged. These CD277-induced additive functional effects are in accordance with the detection of early T-cell activation events such as TCR-induced cell signaling being increased upon CD277 engagement. However, we found that CD277 triggering is not involved in CD16- or NKp46-induced NK cell activation. BTN3/CD277 comprises three structurally related members, BTN3A1, BTN3A2 and BTN3A3. CD277 antibodies recognize all isoforms and we describe a differential expression of BTN3 isoforms between T and NK cells that could explain differential CD277 functions between T and NK cells. Our results show that, while T cells express all BTN3/CD277 transcripts, NK cells express mostly BTN3A2, which lacks the B30.2 intracellular domain. Furthermore, NKp30-induced cytokine production is decreased by the specific engagement of BTN3A2, but not by BTN3A1 triggering. Thus, we provide new insights into the CD277 co-stimulatory pathway that may differentially participate in the regulation of various cell-mediated immune responses.

The regulated release of cytokines from a cell. Cytokines are any of a group of proteins that function to control the survival, growth and differentiation of tissues and cells, and which have autocrine and paracrine activity.

The human butyrophilin (BTN) 3 or CD277 molecules belong to the B7 family members and are expressed in various immune cells such as T and NK cells. Here, we show that CD277 triggering considerably enhances TCR-induced cytokine production and cell proliferation, even when another co-stimulatory molecule, CD28, is engaged. These CD277-induced additive functional effects are in accordance with the detection of early T-cell activation events such as TCR-induced cell signaling being increased upon CD277 engagement. However, we found that CD277 triggering is not involved in CD16- or NKp46-induced NK cell activation. BTN3/CD277 comprises three structurally related members, BTN3A1, BTN3A2 and BTN3A3. CD277 antibodies recognize all isoforms and we describe a differential expression of BTN3 isoforms between T and NK cells that could explain differential CD277 functions between T and NK cells. Our results show that, while T cells express all BTN3/CD277 transcripts, NK cells express mostly BTN3A2, which lacks the B30.2 intracellular domain. Furthermore, NKp30-induced cytokine production is decreased by the specific engagement of BTN3A2, but not by BTN3A1 triggering. Thus, we provide new insights into the CD277 co-stimulatory pathway that may differentially participate in the regulation of various cell-mediated immune responses.

The human butyrophilin (BTN) 3 or CD277 molecules belong to the B7 family members and are expressed in various immune cells such as T and NK cells. Here, we show that CD277 triggering considerably enhances TCR-induced cytokine production and cell proliferation, even when another co-stimulatory molecule, CD28, is engaged. These CD277-induced additive functional effects are in accordance with the detection of early T-cell activation events such as TCR-induced cell signaling being increased upon CD277 engagement. However, we found that CD277 triggering is not involved in CD16- or NKp46-induced NK cell activation. BTN3/CD277 comprises three structurally related members, BTN3A1, BTN3A2 and BTN3A3. CD277 antibodies recognize all isoforms and we describe a differential expression of BTN3 isoforms between T and NK cells that could explain differential CD277 functions between T and NK cells. Our results show that, while T cells express all BTN3/CD277 transcripts, NK cells express mostly BTN3A2, which lacks the B30.2 intracellular domain. Furthermore, NKp30-induced cytokine production is decreased by the specific engagement of BTN3A2, but not by BTN3A1 triggering. Thus, we provide new insights into the CD277 co-stimulatory pathway that may differentially participate in the regulation of various cell-mediated immune responses.

The human butyrophilin (BTN) 3 or CD277 molecules belong to the B7 family members and are expressed in various immune cells such as T and NK cells. Here, we show that CD277 triggering considerably enhances TCR-induced cytokine production and cell proliferation, even when another co-stimulatory molecule, CD28, is engaged. These CD277-induced additive functional effects are in accordance with the detection of early T-cell activation events such as TCR-induced cell signaling being increased upon CD277 engagement. However, we found that CD277 triggering is not involved in CD16- or NKp46-induced NK cell activation. BTN3/CD277 comprises three structurally related members, BTN3A1, BTN3A2 and BTN3A3. CD277 antibodies recognize all isoforms and we describe a differential expression of BTN3 isoforms between T and NK cells that could explain differential CD277 functions between T and NK cells. Our results show that, while T cells express all BTN3/CD277 transcripts, NK cells express mostly BTN3A2, which lacks the B30.2 intracellular domain. Furthermore, NKp30-induced cytokine production is decreased by the specific engagement of BTN3A2, but not by BTN3A1 triggering. Thus, we provide new insights into the CD277 co-stimulatory pathway that may differentially participate in the regulation of various cell-mediated immune responses.

Keywords

Protein involved in adaptive immunity. Vertebrates can develop a broad and almost infinite repertoire of antigen-specific receptors, which allows vertebrates to recognize almost any potential pathogen or toxin and to mount antigen-specific responses to it. Two types of adaptive immunity systems have evolved in vertebrates in order to generate immune receptor diversity. The jawed vertebrates strategy uses the V(D)JC recombination to achieve combinatorial diversity of immunoglobulin-based B cell receptors and T cell receptors. The jawless vertebrate strategy uses the somatic rearrangements of variable leucine-rich cassettes in the variable lymphocyte receptors (VLRs). The hallmarks of an adaptive immune system is the production of antigen-specific recognition receptor by somatic gene rearrangement. The long life of some antigen-primed cytotoxic lymphocytes and plasma cells provide protective memory to prevent reinvasion.

Protein involved in immunity, any immune system process that functions in the response of an organism to a potential internal or invasive threat. The vertebrate immune system is formed by the innate immune system (composed of phagocytes, complement, antimicrobial peptides, etc) and by the adaptive immune system which consists of T- and B- lymphocytes.

Protein which is part of a reference proteome. Reference proteomes are a subset of proteomes that have been selected either manually or algorithmically according to a number of criteria to provide a broad coverage of the tree of life and a representative cross-section of the taxonomic diversity found within UniProtKB, as well as the proteomes of well-studied model organisms and other species of interest for biomedical research.